1. Field of the Invention
The present invention relates to piezoelectric ceramic compositions and piezoelectric ceramic devices using the same. In particular, the present invention relates to piezoelectric ceramic compositions which are useful as materials for piezoelectric ceramic filters, piezoelectric ceramic oscillators and piezoelectric ceramic vibrators, and relates to piezoelectric ceramic devices using the same.
2. Description of the Related Art
Piezoelectric ceramic compositions comprising lead titanate zirconate (Pb(Ti.sub.x Zr.sub.1-x)O.sub.3) or lead titanate (PbTiO.sub.3) as main components are extensively used in piezoelectric ceramic filters, piezoelectric ceramic oscillators and piezoelectric ceramic vibrators. In production of the piezoelectric ceramic compositions comprising lead titanate zirconate or lead titanate as the main components, lead oxide is generally used. Since lead oxide, however, is lost by vaporization during the production steps, the composition of the product is not uniform.
On the other hand, piezoelectric ceramic compositions comprising bismuth layered compounds such as (Ca.sub.1-x M.sub.x)Bi.sub.4 Ti.sub.4 O.sub.15 as main components do not contain lead oxide and do not have the above problem. The bismuth-based piezoelectric ceramic compositions, however, have small electromechanical coupling coefficients kt and are not used in practice.